Analysis:

This quatrain by Saadi Shirazi delves into the nature of human connection and the importance of character.

The Allure of the World: The first line highlights the allure of worldly attractions such as fame, beauty, and material possessions. These things can often captivate human hearts.
The Human Heart: The second line emphasizes that despite these external attractions, the human heart is capable of deep feelings and emotions. It is not as cold and indifferent as a stone.
The Importance of Character: The final two lines underscore the significance of character in human relationships. A person who lacks good nature or virtue will neither be capable of loving nor be loved by others.

Themes:

The Human Heart: The quatrain explores the complexities of the human heart and its capacity for love and connection.
The Importance of Character: It emphasizes that true beauty and worth lie in a person's character.
The Futility of Material Possessions: The quatrain suggests that worldly possessions and fame cannot bring lasting happiness.

Deeper Meaning:

Saadi is suggesting that while external beauty and worldly success may be attractive, they are ultimately superficial. True happiness and fulfillment come from having a good character and being able to form deep, meaningful connections with others. The quatrain serves as a reminder that the human heart is capable of great love and compassion, but it also requires nurturing and care.

This quatrain is a timeless reminder that true beauty lies within, and that lasting relationships are built on mutual respect and understanding.